1. Field
This document relates to a non-glasses type stereoscopic image display device which displays a stereoscopic image by switching multi-view images to their respective multi-view areas by an optical plate.
2. Related Art
A stereoscopic image display device may be classified into a stereoscopic technique and an autostereoscopic technique. The stereoscopic technique is implemented using parallax images of left and right eyes having the most reliable three dimensional effects. The stereoscopic technique is classified into a glasses method and a non-glasses method, both of which are commercialized.
Because of the convenience of allowing users to view stereoscopic images without wearing shutter glasses or polarized glasses, the non-glasses method has been frequently used for small-to-medium sized displays such as smartphones, tablets, or laptops in recent years. The non-glasses method is a method which obtains a stereoscopic image by separating the optical axes of left and right parallax images using an optical plate such as a parallax barrier or a lenticular lens.
In the non-glasses method, a display defect and Moiré pattern may be perceived due to interference between the optical plate 2 of FIG. 1 and a black matrix BM formed on a display panel 1. To avoid the display defect and Moiré pattern, the non-glasses method employs slanted lenses (or slanted barriers) 2 slanting at a predetermined angle from sub-pixels of the display panel 1 to divide multi-view images V1 and V2 into respective view areas, as shown in FIG. 1. As seen from FIG. 1, the use of the slanted lenses 2 can reduce the overlapping regions between the boundary regions BP of the lenses 2 and the black matrix BM, and can therefore reduce the display defect, etc.
However, the conventional non-glasses method using slanted lenses or the like has the problem of dark lines (black stripes) and three-dimensional (3D) crosstalk caused by luminance difference depending on the viewing angle, as shown in FIG. 2. In FIG. 2, the dotted line graph indicates the luminance intensity of a first view image V1 versus viewing angle, and the solid line graph indicates the luminance intensity of a full-white image. Here, the first view image V1 indicates either a left-eye image or right-eye image, and the second-view image V2 indicates the other eye's image.
The angle of refraction of display light entering the slanted lenses 2 from the display panel 1 is relatively large at the edges EG of the slanted lenses 2, compared to that at the centers CEN of the slanted lenses 2. 3D crosstalk occurs when multi-view images are seen as interfering with each other in the user's single eye. To reduce 3D crosstalk, the first view image V1 should be refracted from one side edge of the slanted lenses 2 toward the left eye (or right eye) of the user, and the second view image V2 should be refracted from the other side edge of the slanted lenses 2 toward the right eye (or left eye) of the user, in order to prevent interference between the first view image V1 and the second view image V2 seen in a single eye.
However, the use of the slanted lenses 2 of FIG. 1 causes the sub-pixels for displaying the first view image V1 (or second view image V2) to overlap the left half portion LT and right half portion RT of each of the lenses 2 in a specific area AA of the display panel 1, always making the sub-pixels correspond to the centers CEN of the lenses 2. In this case, a specific view image (V1 of FIG. 1) passing through the centers CEN Of the lenses 2 enters both the left and right eyes of the user, thus causing 3D crosstalk.